Lower Mud Lake, Yahara River and Lake Kegonsa Watershed (LR06)
Lower Mud Lake, Yahara River and Lake Kegonsa Watershed (LR06)
Lower Mud Lake (803400)
184.61 Acres
Natural Community
Natural communities (stream and lake natural communities) represent model results that use predicted flow and temperature based on landscape features and related assumptions. Ranges of flow and temperature associated with specific aquatic life communities (fish, macroinvertebrates) help biologists identify appropriate resource management goals. Wisconsin Natural Communities.
Shallow Lowland
Year Last Monitored
This is the most recent date of monitoring data stored in SWIMS. Additional surveys for fish and habitat may be available subsequent to this date.
This lake is impaired
PFOS Contaminated Fish Tissue
Trout Water 
Trout Waters are represented by Class I, Class II or Class III waters. These classes have specific ecological characteristics and management actions associated with them. For more information regarding Trout Classifications, see the Fisheries Trout Class Webpages.
Outstanding or Exceptional 
Wisconsin has designated many of the state's highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an 'antidegradation' policy that is designed to prevent any lowering of water quality - especially in those waters having significant ecological or cultural value.
Impaired Water 
A water is polluted or 'impaired' if it does not support full use by humans, wildlife, fish and other aquatic life and it is shown that one or more of the pollutant criteria are not met.

Fish and Aquatic Life

Current Use
The use the water currently supports. This is not a designation or classification; it is based on the current condition of the water. Information in this column is not designed for, and should not be used for, regulatory purposes.
Shallow Lowland
Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.
Attainable Use
The use that the investigator believes the water could achieve through managing "controllable" sources. Beaver dams, hydroelectric dams, low gradient streams, and naturally occurring low flows are generally not considered controllable. The attainable use may be the same as the current use or it may be higher.
Aquatic Life
Waters that support fish and aquatic life communities (healthy biological communities).
Designated Use
This is the water classification legally recognized by NR102 and NR104, Wis. Adm. Code. The classification determines water quality criteria and effluent limits. Waters obtain designated uses through classification procedures.
Default FAL
Fish and Aquatic Life - Default Waters do not have a specific use designation subcategory but are considered fishable, swimmable waters.


Rock River Water Quality Management Plan, Lower Rock River Appendix. WT-668-2002. South Central Region, WDNR.

The Yahara River flows from Lake Waubesa into Lower Mud Lake. The lake has a surface area of 195 acres and a maximum depth of 15 feet. In addition to river flow, water sources include groundwater discharge by small springs and seepages from the surrounding marsh. Water quality problems exist as a result of heavy nutrient loads carried into the lake by the Yahara River, from direct runoff from adjacent agricultural fields, and from surrounding urban development. Increasing urbanization and development pressure in the Village of McFarland near the lake is responsible for much of the sediments and nutrients deposited into Lower Mud Lake. Occasional low flow conditions in the lake, likely from the diversion of effluent around the Yahara Lakes, exacerbates water quality problems (Fix 2000, personal communication).
The shallow Lower Mud Lake experiences excessive aquatic plant growth and is used extensively by migrating waterfowl. The open water area of Lower Mud Lake, is an extremely important resting area for migrating waterfowl during the spring. Ducks, geese, herons and swans will stop to rest and feed here. Since the water opens early on the river, the area is especially good for early migrating waterfowl. Fast boat traffic, however, degrades established wetland plants and stir bottom sediment, clouding the water, releasing stored nutrients in sediment, and reducing overall lake and wetland functional values.
Evaluations by South Central Region Lake Management and Nonpoint Source staff characterize this lake and its wetlands as threatened and in need of management and protection. In 1996, Dane County and the Village of McFarland received DNR grants to acquire land to protect the lake. This lake would benefit from protection of existing wetlands and enhancement of buffers.
Commonly found fish species include the longnose gar, bowfin, northern pike, common carp, golden shiner, bluntnose and fathead minnow, white sucker, black, brown, and yellow bullhead, channel catfish, brook silverside, white and rock bass, green sunfish, pumpkinseed, bluegill, largemouth bass, white and black crappie, yellow perch, walleye, and freshwater drum. The lake is predominantly a panfish and bass lake and walleye fishing is negligible. Lack of adequate public access to the lake is a problem.

Date  2002

Author   Aquatic Biologist


The Lower Mud Lake Wetlands that surround Lower Mud Lake act to buffer the wetland from surrounding agricultural lands as well as provide a much needed groundwater recharge area and critical fishery and waterfowl habitat. These wetlands are a part of the many large peat deposits along the Yahara River. The Dane County Regional Planning Commission has ranked this wetland as a Priority I, one of the most important in the county for management and protection.

The wetland on the east side of Lower Mud Lake is a sedge meadow on a deep layer of peat and encompasses about 200 acres. The Department of Natural Resources owns 137 of the 200 acres on the east side. The east wetlands provide breeding and feeding habitat areas for the woodcock and snipe. This wetland extends into the Village of McFarland where it is designated as a park and conservancy area. In two places, arms of this wetland extend eastward to connect with the Door Creek wetlands along Lake Kegonsa. Shrubs, trees and reed canary grass are currently invading this area.

A second wetland area is on the west side of Lower Mud Lake. It is about 400 acres in size and fed directly by springs and partially from overland runoff. This area is a deep peat deposit and has more standing water than the east side wetland. Keenan�s Creek flows into the wetland, and there are many springs and seepages discharging groundwater. USH 51 bisects the west wetland. DNR owns approximately 180 acres of land on the west side of Mud Lake. Together the east and west wetlands serve as buffers around Lower Mud Lake and contribute to its value as an isolated wildlife area.
The Tower Road wetland, the third wetland component of the area, is about 100 acres in size and borders Lake Waubesa. This area is similar in character and size to the west side wetland along Mud Lake. It is primarily an emergent wet meadow with some areas of scrub vegetation on wet soils.
The only significant development along Lower Mud Lake is the development of five residential sites on Rivercrest Road, outside of McFarland. Fast boat traffic in Lower Mud Lake impairs wetland plant growth and releases nutrients from the lake sediments reducing the wetland�s functions.
As a major wetland area along the Yahara River, Lower Mud Lake is a significant environmental feature in this watershed. In 1994, Dane County Board of Supervisors adopted the Lower Mud Lake Resource Protection Project Plan prepared by the Dane County Parks Commission and the Dane County Regional Planning Commission. The objectives of the plan are to 1) create a 1,700 acre preserve to protect and restore natural resources such as wetland, floodplain, springs and other related features, 2) provide for and protect natural habitat for fish, waterfowl and wildlife, and 3) preserve archeological and historic resource sites.

These wetlands provide critical fish habitat and spawning grounds for fish in Lower Mud Lake and the Yahara River. Northern Pike move upstream from Lake Kegonsa to spawn in these wetlands. Walleyes are also present in this area during spawning season. Largemouth bass and northern pike are the dominant predator species, while bluegills and black bullheads are the most numerous panfish.

Date  2002

Author   Aquatic Biologist

Historical Description

Source: 1985, Surface Water Resources of Dane County,WI: WI-DNR Lower Mud Lake - T6N, R10E, Sec. 10

This shallow lake is located on the Yahara River and is completely encircled by shallow marsh and fresh meadow. Water quality problems are a result of direct runoff from adjacent agricultural lands and the large nutrient load carried by the Yahara River. Shallowness, excessive aquatic vegetation, poor water quality, and lack of good public access limit the recreational value of this lake. Major fish species include panfish and bullheads, though most species common to the Yahara River system are present. A wilderness type access is available through public hunting grounds on the eastern shore and boats may reach the lake by way of the Yahara River. Waterfowl use of this shallow lake is extensive and hunting is good. Fish species: longnose gar, bowfin, northern pike, common carp, golden shiner, bluntnose and fathead minnow, white sucker, black, brown, and yellow bullhead, channel catfish, brook silverside, white and rock bass, green sunfish, pumpkinseed, bluegill, largemouth bass, white and black crappie, yellow perch, walleye, and freshwater drum.

Surface acres = 195, SDF = 1.23, Maximum depth - 15 ft

Date  1985

Author   Surface Water Inventory Of Wisconsin

Lower Mud Lake, Yahara River and Lake Kegonsa Watershed (LR06) Fish and Aquatic LifeLower Mud Lake, Yahara River and Lake Kegonsa Watershed (LR06) RecreationLower Mud Lake, Yahara River and Lake Kegonsa Watershed (LR06) Fish Consumption

Impaired Waters

Lower Mud Lake was placed under a special fish consumption advisory for PFOS in 2020; this lake was added to the 2022 Impaired Waters List for PFOS in fish tissue.

Date  2022

Author  Ashley Beranek


Wisconsin has over 84,000 miles of streams, 15,000 lakes and milllions of acres of wetlands. Assessing the condition of this vast amount of water is challenging. The state's water monitoring program uses a media-based, cross-program approach to analyze water condition. An updated monitoring strategy (2015-2020) is now available. Compliance with Clean Water Act fishable, swimmable standards are located in the Executive Summary of Water Condition in 2018. See also the 'monitoring and projects' tab.



Lake Classification
Dane County Lake Classification-Phase 2: The Phase 1 classification grant classified all county lakes and streams. This grant will take the next step by developing a management program based on the classification.
Lake Classification
Dane County Department of Planning and Development will hire a project staff in order to develop a Lake Classification project, which is seen as the first step toward developing a consistent set of county-wide standards and procedures to protect Dane County Waters.
Land Acquisition
Dane County shall participate in the Lake Protection Grant Program by purchasing 95 acres of land for public outdoor recreation.

Management Goals

Wisconsin's Water Quality Standards provide qualitative and quantitative goals for waters that are protective of Fishable, Swimmable conditions [Learn more]. Waters that do not meet water quality standards are considered impaired and restoration actions are planned and carried out until the water is once again fishable and swimmable

Management goals can include creation or implementation of a Total Maximum Daily Load analysis, a Nine Key Element Plan, or other restoration work, education and outreach and more. If specific recommendations exist for this water, they will be displayed below online.


Monitoring the condition of a river, stream, or lake includes gathering physical, chemical, biological, and habitat data. Comprehensive studies often gather all these parameters in great detail, while lighter assessment events will involve sampling physical, chemical and biological data such as macroinvertebrates. Aquatic macroinvertebrates and fish communities integrate watershed or catchment condition, providing great insight into overall ecosystem health. Chemical and habitat parameters tell researchers more about human induced problems including contaminated runoff, point source dischargers, or habitat issues that foster or limit the potential of aquatic communities to thrive in a given area. Wisconsin's Water Monitoring Strategy was recenty updated.

Grants and Management Projects

Monitoring Projects

Watershed Characteristics

Mud Lake is located in the Yahara River and Lake Kegonsa watershed which is 126.33 mi². Land use in the watershed is primarily agricultural (54.90%), grassland (10.70%) and a mix of wetland (10.30%) and other uses (24.20%). This watershed has 145.73 stream miles, 3,600.04 lake acres and 6,832.19 wetland acres.

Nonpoint Source Characteristics

This watershed is ranked Medium for runoff impacts on streams, Low for runoff impacts on lakes and High for runoff impacts on groundwater and therefore has an overall rank of High. This value can be used in ranking the watershed or individual waterbodies for grant funding under state and county programs.However, all waters are affected by diffuse pollutant sources regardless of initial water quality. Applications for specific runoff projects under state or county grant programs may be pursued. For more information, go to surface water program grants.

Natural Community

Lower Mud Lake is considered a Shallow Lowland under the state's Natural Community Determinations.

Natural communities (stream and lake natural communities) represent model results and DNR staff valiation processes that confirm or update predicted conditions based on flow and temperature modeling from historic and current landscape features and related variables. Predicated flow and temperatures for waters are associated predicated fish assemblages (communities). Biologists evaluate the model results against current survey data to determine if the modeled results are corect and whether biological indicators show water quaity degradation. This analysis is a core component of the state's resource management framework. Wisconsin's Riverine Natural Communities.

Shallow lowland lake describes the depth and location of the lake in a watershed. These variables affect the lakes response to watershed variables.